Metal salts of acylated aminothiophenols as catalytic plasticizers for rubber



United States Patent METAL SALTS 0F ACYLATED AMINOTHIO-.

PHENOLS AS CATALYTIC PLASTICIZERS FOR RUBBER Edwin 0. Hook, New Canaan,and Arnold R.

Riverside, Conn., assignors to American Cyanamid Company, New York, N.Y., a corporation of Maine No Drawing. Application October 22, 1953,Serial No. 387,775

6 Claims. (Cl. 260-43473) This invention relates to "a new 'plasticizerfor elastom'eric compositions, to plasticizing elastomeri'c compositionsand to compositions so produced.

Davis, j

One procedure for plasticizing or softening rubber or synthetic rubberscomprises the use of small amounts of chemicals. For example, some ofthe aromatic mercaptans and certain nitroso compounds can be utilizedunder suitable conditions to produce the desired etlect While the exactnature of their action is not completely understood, the use of thesechemical plasticizers or peptizers is common. It is with theirmanufacture and use that the present invention is concerned.

In the past, known plasticizers have been objectionablev for one or moreof several reasons. Some, for instance, are not suitably compatible withvarious elastomers. Others are toxic. Many are either skin irritants orskin sensitizers and are objectionable to those obliged to handle thematerial. Others are characterized by very disagreeable odors which areoften imparted to finished 0 articles. Some are not sufficientlyelfective atthe relative low temperatures of the open mill. Still othersare too unstable on storage. Moreover, some materials etfective in theprocessing of natural rubber are'foun'd to be ineffective for softeningsynthetic rubber-like polymers.

As a result, suitable plasticizers are limited in spite of the widedemand for materials adapted for this purpose. It is the primary objectof this invention, there fore, to provide a new class of plasticizers.Such plasticizers should be substantially free of the various objectionsnoted above. In addition, they should be elfective not only in thetreatment of natural rubber, but also in the treatment of syntheticrubber-like polymers such, for example, as copolymers of butadiene andstyrene, bum diene and acrylonitrile and the like. a

In general, the plasticizers forming the present invention comprisemetal salts of acyl'ated aminothiophenols of the formula NHC O-R where Ris an alkyl or alkoxy radical of 1-12 carbon atoms; an aryl radical of6l2 carbon atoms such as An outstanding feature is the eflectiveness ofthese compounds at the relatively low temperatures of the open mill.While the amount of plasticizer is not critical,

polymers of bu'tadiene 1,3 with styrene or 'acrylonitrile.

nevertheless a decided advantage of this invention resides in the factthat superior results are obtained using substantially less plasticizerthan that necessary to obtain the most satisfactory results using themore elfective of the commercially available plasticizers. :In general,amounts as little as 0.01 part per hundred parts of elastomer may beeffectively employed. The actual amount employed depends on theparticular compound, the particular elastomer and the extent ofsoftening desired. In gen- -eral, amounts employed may vary from 0.01 to5 parts .per .100 parts :of elastomer.

,Preparation of this series of compounds may be illustrated by thefollowing examples which are intended only as illustrative and not byway of limitation. All parts are by weight unless otherwise noted.

S MZn 45.6 parts of 0,0-dibenzamidodiphenyldisulfide and 7.2 parts ofzinc dust with one part of a commercial Wetting agent sold under thetrade-mark of U-ltrawet 30 DS were slurfied in parts of methanol andwarmed slightly. 0.8 parts of concentrated hydrochloric acid were thenadded, the mixture refluxed for 1 /2 hours and then filtered, leavingless than one part of gray insolubles. The filtate was poured into iceWater and resultant precipitate collected, washed and dried. Driedprecipitate was slurried in benzene and dried in vacuum over phosphorous.pentox'ide. M. P. 16'5-177 0.; yield 92.6%; percent N: calc. 5.38,found 5.2; percent Zn: calc. 12.48, found 123.

EXAMPLE 2 Zinc o-acetamidothiophenate The procedure of Example 1 wasfollowed using 52 parts of o,o-diacetamidodiphenyldisulfide, 11 parts ofzinc dust and 09 part of concentrated hydrochloric acid. The productobtained melted at 280 C. percent N: calc. 7.06, found 6.57.; percentZn': calc. 16.3, found 16.5.

EXAMPLE 3 Zinc o-IZ-furoylamido) thiophenate i ii i i NC-C on 13.1 partsof -o,o'-dithi-obis(Z-furoylanilide) and 2.1 parts-of zinc dust wereslurried in 50 parts of methanol and -7.parts of-concentratedhydrochloric acid. Resultant slurry was refluxed for 50 minutes andfiltered. The filtrate was added to ice water, filtered again andprecipitate collected, washed and "dried. Precipitate was reslurried inchloroform and dried over phosphorous entoside in vacuum. P. 158180 (2.;percent N: calc. 5.59, found 3.39; percent Zn: calc. 13, found 12.6.

EXAMPLB'4'--- Table II Zmc o-(carbethoxyamido)thiophenate sample Numberi 5 1 2 3 4 5 N--i3O-C1HJ Smoked Sheets 100 100 100 100 100 S.%ZnDlbenzamtdodt heuyldlsulfide-. 0.125 Zn o-benzaml othiophenate... 0.09410 Zn o-carbethoxyamldothlophenote 0.0025 The procedure of Example 1 wasfollowed using 19.6 g gzg y 0625 parts ofo,o-di(carbethoxyamido)diphenyldisulfide, 3.6 Mooney i gg at parts of21116 dust, 0.7 part of concentrated hydrochloric 62 44 4L5 acid and 130parts of methyl alcohol. The product obtained had a M. P. of 1l813l C.percent N: calc. 6.14%, found 6.01; percent Zn: calc. 14.2, found 13.46.

EXAMPLE 5.

Zinc o-(carboisobutoxyamido) thiophenate ll N-C-O-CHaCHUJHr):

The procedure of Example 1 was followed using 112 parts ofdi(carboisobutoxyamido)thiophenate, 16.9 parts of zinc dust, 0.2 part ofconcentrated hydrochloric acid and 375 parts of methyl alcohol. Productmelted at 96-l19 C. percent N: calc. 5.46, found 5.10; percent Zn: calc.12.65, found 11.8.

The following examples illustrate the plasticizing effect 4 of thecompounds of this invention on natural rubber and GR-S-ISOO (80%butadiene and 20% styrene made at 41 F.). Testing was done in a Mooneyshearing disc plastometer.

The lower the reading the greater the plasticity. All parts are byweight unless otherwise noted.

EXAMPLE 6 Samples of natural rubber were milled for 10 minutes at 212 F.with various zinc salts of acylated aminothiophenols using as blanks asample with no plasticizer and The above table shows the products ofthis invention to The readings in the examples are viscosity 3 readingsafter 4 minutes in the plastometer at 212' F.

Table II clearly shows that superior results are obtained at low millingtemperatures with relatively smaller amounts of the compounds of thisinvention than with commercially available dibenzamidodiphenyldisulfide.

EXAMPLE 8 Samplesof GR-S-ISOO (80% butadicne and 20% styrene) weremilled at 100 C. for 10 minutes with varying amounts of zinco-(carboisobutoxyamido)thiophenate and using similar blanks as inExamples 6 and 7.

Table III Sample Number GR-S-1500 100 100 100 100vDlbenzarnldodlphenyldisultide 1.5 Zn o-carboisobutoxynmldothiophenato0.75 1.5 Mooney viscosity 212 F. (ML-4) 49. 5 47 35. 6 32. 5

NBC O-R in which R is selected from the group consisting of alkyl andalkoxy radicals of 1-12 carbon atoms, aryl radicals of 6-12 carbonatoms, and heterocyclic radicals selected ,from the group consisting offuryl, thienyl, pyrrolidyl give improved softening effect overdibenzamidodiphenyldisulfide, one of the more superior commerciallyavailable plasticizers.

EXAMPLE 7 Example 6 was repeated varying the amounts of plasand pyridyl.

2. Zinc o-(carboisobutoxyamido)thiophenate having the formula 3. Zinco-tczlrbcthoxyamido)thiophenate having the formula 4. Zinco-benzamidothiophenate having the formula 5 Zinco-(2-furoylamido)thiophenate having th: formula H o HC-FH M41 1H 5 S-MZn6. Zinc o-acetamidothiophenate having the formula O T-JL-CH:

References Cited in the file of this patent UNITED STATES PATENTSVerbanc Apr. 19, 1949 Paul May 24, 1949 Patrick etal. Nov. 18, 1952Lober Nov. 30, 1954 OTHER REFERENCES

1. ZINC SALTS OF ACYLATED AMINOTHIOPENOLS HAVING THE TYPE FORMULA 5.ZINC O-(2-FUROYLAMIDO) THIOPHENATE HAVING THE FORMULA